Eyedrivomatic uses an arduino to control two servos. For the servo power i want to use a cheap usb battery pack, of the sort used for emergency charging of mobile phones. The arduino itself is powered through the usb cable (which is always connected). My problem is that the power packs automatically shut down when there is no drain, ie. when the servos aren't moving. They don't then turn back on when the servos want to move again. Very irritating. I am currently using more expensive battery packs with physical on/off switches, but want to reduce the costs for other users. What i need is a way to fool the battery pack into staying on regardless of whether the servo is moving or not.

If my hands worked i would tinker with it until i found a solution, but they don't. I'm a quadraplegic, and have to rely on my carers for all physical tasks.

hi Kumar. Thanks for your reply. I like your battery project. If that was a manufactured product, i would buy one instantly. I love the concept. Another product i tried is a jump starter battery. Same issue. What i'm looking for is a readily available, off the shelf, rechargeable portable power pack. And there just isn't one. If you have any further ideas about the usb power packs i would be grateful..

brilliant! Thanks Luke. I knew the solution wouldn't be simple. Your approach makes sense, and i will investigateit further. I am currently franticly building systems for our first round of beta testers. So, when thats done, i'll get back to thebattery problem.

Eyedriveomatic is a really awesome project! I'm happy to provide some advice. I do think that this issue can be defeated however to be honest, it isn't going to be pretty. Like you said, the battery pack is shutting down when it does not see a current draw, this is an effort to save power.

I think without getting into the pack and hacking it (which would not be desirable from a manufacturability point of view), you would need to have a minimum amount of current draw in your circuit to keep the regulator running. This is sort of a waste of power, probably not a good thing to do.

You could wire this directly into the X1 connector on the Arduino and it would work. With that said, Uno has a Linear regulator here so this may be less efficient than you would like. This is easially solved with a buck regulator module such as this: http://www.digikey.com/product-detail/en/TR05S05/1470-2254-5-ND/4488633 then you can supply a regulated 5V to all of your circuits and it won't shut down until the battery dies. You will find that this configuration to last an incredibly longer amount of time.